The present invention relates to a method and apparatus for testing subsystem and/or system performance of an electronic printer, and more particularly, to a method and apparatus for testing subsystem and/or system performance of an electronic color printer using selected portions of an electronic scanning system (ESS) bitmap representing an image to be printed as a virtual test pattern.
Conventional imaging process control systems often generate separate images or patches to be read by various sensors, such as an electrostatic voltmeter (ESV), an infrared densitometer (IRD), toner area coverage sensor (TAC), densitometer, colorimeter, etc. Each of the sensors is adapted to sense attributes of the image throughout the imaging process. The sensor output is used for the purpose of characterizing subsystem performance as part of a closed loop control system.
In an office environment, sensing is typically limited to subsystems prior to the transfer step; the resulting untransferred images can impose unwanted stresses on the cleaning system. This is because post-transfer sensing requires the printing of control images or test patches on the output prints or on special test prints. Clearly, an operator would object to such images or patches on their output.
Frequently, the marking engine of an electronic reprographic printing system is an electrophotographic printing machine. In an electrophotographic printing machine, a photoconductive member is charged to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is exposed. Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document being reproduced. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing toner into contact therewith. This forms a developed toner image on the photoconductive member, which is subsequently transferred to a copy sheet. The copy sheet is heated to permanently affix the toner image thereto in image configuration.
Multi-color electrophotographic printing is substantially identical to the foregoing process of black and white printing. However, rather than forming a single latent image on the photoconductive surface, successive latent images corresponding to different colors are recorded thereon. Each single color electrostatic latent image is developed with toner of a color complimentary thereto. This process is repeated a plurality of cycles for differently colored images and their respective complimentarily colored toner. In some applications each single color toner image is transferred to an intermediate member or to the copy sheet in superimposed registration with the prior toner image. In other applications all four separations may be transferred simultaneously to the final copy sheet. This creates a multi-layered toner image on the copy sheet. Thereafter, the multi-layered toner image is permanently affixed to the copy sheet creating a color copy. The developer material may be a liquid material or a powder material.
U.S. Pat. No. 5,019,859 granted to Thomas W. Nash on May 28, 1991 relates to a highlight color imaging apparatus and method for creating highlight color images that allows the inter-image areas to be used for developability or other control functions notwithstanding the necessity of developer switching. The black and highlight color images are separately formed and the order of image formation is one where the black image (B1) for the first copy is formed, followed by the highlight color image (C1) for the first copy; then the highlight color image (C2) for the second copy; then the black image (B2) for the second copy; then the black image (B3) for the third copy and finally the highlight color image (C3) for the third copy. With the foregoing order of image creation, developer switching is not required when two adjacent images are the same color. When developer switching is not required, the inter-image area can be used for process control such as developability to form a test pattern. Thus, in the example above, the area between the two adjacent color images (C1,C2) is available for forming a color test patch. Likewise, the area between the two black images (B2,B3), is available for forming a black test patch.